I. Field of the Invention
This invention relates generally to methods and apparatus for transforming thermal energy from a heat source into mechanical and then electrical form using a working fluid that is expanded and regenerated. This invention further relates to a method and system for improving the thermal efficiency of a thermodynamic cycle via the generating of at least two multi-component liquid working streams, including a rich stream and a lean stream. The rich stream includes a higher percentage of a low-boiling component than is included in the lean stream.
II. Brief Description of the Background Art
U.S. Pat. No. 4,548,043 describes a system that uses two different streams of working solution with different compositions. That system includes means for heating and expanding a working fluid and a condensation subsystem for condensing that working fluid and generating the two streams having different compositions.
The condensation subsystem described in that patent generates from a single partially evaporated stream, comprising a mixture of ammonia and water, a single enriched vapor stream and a single lean liquid stream. The enriched vapor stream is divided into two enriched vapor substreams. The lean liquid stream is divided into two lean liquid substreams. One of those enriched vapor substreams is combined with one of the lean liquid substreams producing a rich stream. The other enriched vapor substream is combined with the other lean liquid substream producing a lean stream. Because the two enriched vapor substreams are generated from a single enriched vapor stream, they are each generated at the same pressure and temperature. The two working streams generated from combining the two vapor substreams with the two liquid substreams in U.S. Pat. No. 4,548,043, i.e., the rich stream and the lean stream, are combined during the boiling process.
U.S. Pat. No. 4,604,867 likewise describes a system that includes means for evaporating and expanding a working stream followed by condensing that expanded stream via a condensation subsystem. The condensation subsystem described in that patent, like that included in U.S. Pat. No. 4,548,043, generates an enriched vapor stream and a lean liquid stream from a single partially evaporated multi-component stream. The vapor stream is combined with a portion of the liquid stream to produce the working stream that is subsequently evaporated and expanded.
The systems of U.S. Pat. Nos. 4,548,043 and 4,604,867 provide significantly enhanced thermal efficiency, when compared to conventional Rankine cycles that use a single component working fluid. However, it is always desirable to improve upon the economics and efficiencies of such systems. The method and system of the present invention, when compared to the systems described in the above-mentioned patents, provides such an improvement.